| JIMOH Rasheed Olayinka,TANG Yong,LI Jiabiao,AWOSIKA Larry Folajimi,LI He,AKINNIGBAGE Edward Akintoye,ADELEYE Adedayo Oluwaseun. 2018. The architecture of the lower parts of submarine canyons on the western Nigerian continental margin. Acta Oceanologica Sinica, 37(7):28－40 |
| The architecture of the lower parts of submarine canyons on the western Nigerian continental margin |
| 尼日利亚西部大陆边缘海底峡谷下部结构研究 |
| Received:July 17, 2017 |
| DOI：10.1007/s13131-018-1242-0 |
| Key words:western Nigerian continental margin submarine canyons architecture controlling factors sedimentary processes tectonic evolution |
| 中文关键词: 尼日利亚西部大陆边缘 海底峡谷 控制因素 沉积过程 断层作用 |
| 基金项目:The National Natural Science Foundation of China under contract No. 41470648; the Public Science and Technology Research Funds Projects of Ocean under contract No. 201205003; the National Program on Global Change and Air-Sea Interaction, SOA under contract No. 631 GASI-GEOGE-01. |
| Author Name | Affiliation | E-mail | | JIMOH Rasheed Olayinka | Ocean College, Zhejiang University, Zhoushan 316021, China
Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
Key Laboratory Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China
Nigerian Institute for Oceanography and Marine Research, Lagos PMB 12729, Nigeria | | | TANG Yong | Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
Key Laboratory Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China | tangyong@sio.org.cn | | LI Jiabiao | Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | | | AWOSIKA Larry Folajimi | Commission on the Limits of the Continental Shelf, C/O Division of Ocean Affairs and Law of the Sea, New York 11101, United Staters | | | LI He | Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
Key Laboratory Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China | | | AKINNIGBAGE Edward Akintoye | Ocean College, Zhejiang University, Zhoushan 316021, China
Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
Nigerian Institute for Oceanography and Marine Research, Lagos PMB 12729, Nigeria | | | ADELEYE Adedayo Oluwaseun | Ocean College, Zhejiang University, Zhoushan 316021, China
Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
Nigerian Institute for Oceanography and Marine Research, Lagos PMB 12729, Nigeria | |
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| Abstract: |
| Multi-beam, sub-bottom and multichannel seismic data acquired from the western Nigerian continental margin are analysed and interpreted to examine the architectural characteristics of the lower parts of the submarine canyons on the margin. The presence of four canyons:Avon, Mahin, Benin, and Escravos, are confirmed from the multi-beam data map and identified as cutting across the shelf and slope areas, with morphological features ranging from axial channels, moderate to high sinuosity indices, scarps, terraces and nickpoints which are interpreted as resulting from erosional and depositional activities within and around the canyons. The Avon Canyon, in particular, is characterised by various branches and sub-branches with complex morphologies. The canyons are mostly U-shaped in these lower parts with occasional V-shapes down their courses. Their typical orientation is NE–SW. Sedimentary processes are proposed as being a major controlling factor in these canyons. Sediments appear to have been discharged directly into the canyons by rivers during the late Quaternary low sea level which allows river mouths to extend as far as the shelf edge. The current sediment supply is still primarily sourced from these rivers in the case of the Benin and Escravos Canyons, but indirectly in the case of the Avon and Mahin Canyons where the rivers discharge sediments into the lagoons and the lagoons bring the sediments on to the continental shelf before they are dispersed into the canyon heads. Ancient canyons that have long been buried underneath the Avon Canyon are identified in the multichannel seismic profile across the head of the Avon Canyon, while a number of normal faults around the walls of the Avon and Mahin Canyons are observed in the selected sub-bottom profiles. The occurrence of these faults, especially in the irregular portions of the canyon walls, suggests that they also have some effect on the canyon architecture. The formation of the canyons is attributed to the exposure of the upper marginal area to incisions from erosion during the sea level lowstand during the glacial period. The incisions are widened and lengthened by contouric currents, turbidity currents and slope failures resulting in the canyons. |
| 中文摘要: |
| 通过对在尼日利亚大陆边缘西部获取的多波束、浅层剖面和多道地震数据的分析解译，我们研究了该陆缘海底峡谷下部的形态特征。确定并识别出四个海底峡谷：Avon峡谷、Mahin峡谷、Benin峡谷和Escravos峡谷，这些峡谷均穿过陆架-陆坡区，河道的地貌特征变化从轴向到中等弯度，再到高弯度，并有陡崖、阶地以及裂点现象，研究认为是峡谷内及周缘侵蚀活动和沉积活动的结果。其中，Avon峡谷具有较多的分支和子分支，地貌特征复杂，沉积物可能在晚第四纪低海平面期间被一直延伸到大陆架外缘的河流直接排入这些峡谷之中。对于Benin峡谷和Escravos峡谷，现代沉积物的供给依然大部分来源于陆上河流，但在Avon和Mahin峡谷中，河流输送物源则是在其排入峡谷头部之前，河流首先将沉积物排入泻湖，再由泻湖将沉积物带进大陆架。因此研究区峡谷形成的原因是由于在海平面处于低水位冰期，该陆缘上层地壳出露，受到侵蚀作用而产生切口，这些切口又在多幕等深流、浊流和滑坡破坏作用下转化为峡谷。所有峡谷的主要走向为NE-SW向，与主要断裂、断裂带的走向一致，而这些断裂和断裂带对这些峡谷的演化和稳定有一定的控制作用。 |
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